There is something deeply chilling when a young, apparently fit, professional footballer can suddenly be face down on the turf and it is very apparent, just from the speed at which people are moving around him, the urgency of their body language and the way the other players are reacting, crying, praying, barely able to watch, that this is absolutely terrible.

Fabrice Muamba was having a decent game for Bolton Wanderers in their FA Cup tie at White Hart Lane. Nothing too spectacular, but that is not his kind of style anyway. We are talking here about the classic midfield type, winning the ball, laying it off, quick to get back when the other side had possession. Disciplined, energetic, combative. And then, suddenly, inexplicably, lying on the grass, eyes closed, without a single player anywhere near him. Those are the moments when everything goes into slow-motion and it is impossible to feel anything but helpless.

Everything had been so innocent a few hours earlier when the Bolton team coach inched through the gates at White Hart Lane and Muamba posted a message on Twitter letting his followers know the players were in place, followed by the hashtag COYW – meaning 'Come on you Whites'. This was a young man, still three weeks away from his 24th birthday, looking forward to playing at a ground that is no more than three miles away from where he went to school.

Within hours, Twitter had become the online equivalent of a hospital waiting room. "Pray for Muamba" was trending and it was very clear from the messages of so many people within the game that we are talking here about a popular and likeable member of every dressing room where he has ever played. Everyone who has spoken about Muamba from first-hand experience has said roughly the same things: that he is always smiling, a loyal friend, someone who will do anything to help the people who are close to him and, in a professional sense, exudes a quiet determination to make the most of his career.

The first time I met him was at Birmingham City's training ground four years ago. Muamba had just signed from Arsenal for £4m and, as tends to happen when a black guy has that long, leggy stride and plays in central midfield, he was being talked about as the new Patrick Vieira. If that was the case, Arsène Wenger would never have let him go. But Muamba had already represented England's Under-21s by then and it did not seem out of place, at the age of 20, that he should speak about wanting to win senior caps and play in big international tournaments.

He was confident enough, but certainly not cocky, and even a little uncertain at first about why anyone would want to interview him. More than anything, there was something very likeable about him. Muamba was different to the average Premier League footballer. Little things like being on time and thanking me for making the journey to see him. He did not have his agent with him and he didn't treat every question like a trap. At the end, he wanted to know when it was going to be published because it would be nice to keep a copy for his mum.

This was the first time he had lived alone and it transpired he had been watching Ready Steady Cook to try to teach himself how to drum up a few meals.

But it was when Muamba opened up that it became clear he had a remarkable story to tell and that, for all the innocent little jokes about boiled eggs and culinary disasters, this was a young man who had grown up in Kinshasa, in the Democratic Republic of Congo, and had seen, close-up, the brutality of one of the bloodiest civil wars in history.

It became clear that the only reason Muamba was in England is because his father, Marcel, was a political refugee, granted indefinite leave on the basis that his life would be in danger if he were made to return to Africa. Muamba talked of going to sleep at night amid the backdrop of gunfire. His uncle, Ilunga, was murdered. Friends and neighbours died, too. When it was safe, he and his friends would play football but, very often, they would be called back inside.

Marcel had to leave the country because the alternative, almost certainly, was that he would be found and killed. He had been a politician affiliated to President Mobotu Sese Seko's government and that made him an obvious target when the anti-Mobutu rebels combined to form the Alliance of Democratic Forces for the Liberation of Zaire. So he took his family to Ilunga's house then fled for England, living in detention centres and fighting the system until he was granted asylum.

"He just came in to see me one morning and told me he was going out," Muamba said. "I asked him where but he just said he had to go. I said, 'OK, see you when I see you.' I didn't realise he was going to the airport and leaving."

They did not see each other for three years until Marcel's wife, Gertrude, arrived at Heathrow with an 11-year-old Fabrice. "It was 6 December 1999, and it was the kind of coldness I had never known. It was the first time I had seen snow. I was shivering when I got off the plane but it was worth it. We saw my father and we all ran up to each other and started hugging. It was the start of our new life."

The young Muamba did not speak a word of English when he arrived in London and was so scared of making a fool of himself at school in Waltham Forest he would go for hours without speaking. Even when he learned the language he seldom talked of his past and almost never about what happened to Ilunga. "Nobody has ever told me what exactly happened and I don't ask because I don't want to know," he told me. "All I know is that he was killed."

He made his friends at school through playing football. He had reached 6ft by the age of 14 and Arsenal got to hear about him when he asked for a trial. Muamba was fast-tracked through the club's academy system and, at 17, made his first-team debut in a Carling Cup tie against Sunderland in October 2005. A season-long loan was arranged with Birmingham in 2006-07 and eventually Steve Bruce, then the manager at St Andrews, persuaded Wenger to let him go.

Muamba played at Birmingham only a year before signing for Bolton, for £5m, in 2008. He was the Bolton News' player-of the year in 2010 and the game at Spurs was to take him one appearance shy of his 150th match for the club. Perhaps, one day, he will make it to that point and beyond. For now, though, we can only hope. Muamba has a young son, Joshua, and got engaged to Shauna, his girlfriend, on Valentine's Day. Vincent Kompany, one of countless footballers to express their emotions via Twitter, summed it up: "Too young to die."

• This article was amended on 20 March 2012. The original referred to President Mobutu Sese Soko. The spelling of his name has been corrected.